RU2701026C1 - Elastomeric oil bitumen modifier and elastomer-bitumen binder based thereon - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: group of inventions relates to elastomer modifiers of oil bitumen, obtained from rubber articles technical articles, which can be used for making elastomer-bitumen binder, and also relates to elastomer-bitumen binder made using said modifiers and intended for use, mainly in road and civil construction for asphalt concrete road surfaces, construction of aerodromes. Elastomeric oil bitumen modifier is a granular regenerate of crumbs of rubber articles, preferably, crumbs from amortized tires (tire regenerate), having following characteristics: content of gel-fraction 73–85 %, weight-average molecular weight of rubber in ash 87,500–131,600 conv. units, weight ratio of rubber is not less than 50 %. Granules with size of 0.5–1.0 mm are preferable. It is also possible to produce granules of said size and / or agglomerates thereof with maximum size of 10–12 mm. Elastomer-bitumen binder contains the claimed elastomeric modifier of oil bitumen and petroleum bitumen, at the following ratio of components, wt%: elastomeric modifier (preferably, tire regenerate) 5–25, petroleum bitumen – the rest – up to 100.

EFFECT: achieved technical result consists in improvement of complex of consumer properties of elastomer-bitumen binder, namely in increase of hardness, softening temperature, elasticity and reduction of brittleness temperature, and, accordingly, improvement of characteristics of asphalt concrete.

5 cl, 2 tbl

Description

The group of inventions relates to elastomeric modifiers of petroleum bitumen from regenerates of rubber products, which can be used for the manufacture of elastomeric-bitumen binders, and also relates to the elastomeric-bitumen binders based on the above modifiers, and is intended for use mainly in road and civil engineering for asphalt concrete pavements of roads, construction of airfields, etc.

The most important condition for increasing the durability of asphalt concrete coatings is to improve the properties of bitumen. However, the deep processing of oil at modern refineries in order to increase the yield of fuel and oils has led to a deterioration in the quality of oil bitumen and their inconsistency with the requirements of road construction in terms of low temperature crack resistance, heat resistance, elasticity and adhesive properties. One of the effective ways to improve the quality of bitumen is to modify it with polymers.

Currently, in the foreign and domestic practice, the so-called “wet method” is used to modify oil bitumen as a priority, which provides for the preliminary production of polymer bitumen binders (PBB) by adding polymer additives - modifiers to heated bitumen.

Known modifiers of bitumen based on various synthetic rubbers (butadiene-styrene, butyl, ethylene propylene and others) having a weight average molecular weight (M _w ) of from 200,000 to 700,000 srvc. units added to bitumen in the amount of 2-7% by weight of bitumen. For example, the gel-like polymer modifier “Caudest-D” (TU 2257-004-01393728-00) [http://www.topomatic.ru/reviews/53-%ABKaudest-D%BB-polimernaja-dobavka-dlja-prigotovlenija- modificirovannyh-vjazhushih-] is a mixture of synthetic commodity rubbers of a linear structure, an adhesive component and stabilizing additives.

Another well-known rubber modifier “Modmel” (TU 2294-009-41993527-98) is made on the basis of ethylene-propylene rubber and additives modifying its properties. The granulated modifier Modmel consists of ethylene propylene diene rubber - 90% and polypropylene - 10%.

Common disadvantages of modifiers using synthetic rubbers are the complexity of manufacturing due to the length and multi-stage process of production of binders, the use of plasticizers and the use of high temperature. These factors contribute to the aging of bitumen at the stage of preparation of bitumen-rubber binders.

Also known are polymer bitumen modifiers made using crumb rubber and rubber products, in particular cushioned tires.

Known modifier of bitumen (RU 2158742, publ. 10.11.2000 g), including bitumen, oil road BND 60/90 or PND 90/130 50-80% of the _mass , pre-partially degraded in the bitumen rubber crumb, which is a waste of rubber production 10-25% _mass and polyisoprene rubber SKI-3 1-5% by _weight polyethylene (LDPE) or a triple copolymer of ethylene with propylene and dienes - SKEPT-40 1-10% by _weight , mineral oil 1-15% by _weight . The bitumen modifier described in RU 2158742 is obtained in the form of a solid, non-sticky mass, which is cut into pieces and introduced in a predetermined ratio into the heated bitumen directly at the site of road or construction work.

The same patent (RU 2158742) describes a binder, which is obtained by adding the specified modifier to the road bitumen in a ratio of 10-20 wt. including modifier 90-80 wt. h. bitumen.

The disadvantages of the modifier according to patent RU 2158742 are due to the use of rubber SKI-3, the Mooney viscosity of which is 75-85 conv. units, which reduces technological properties due to the presence of dense heterogeneous inclusions in crude rubbers. Such inclusions violate the uniformity of the mixture. Another disadvantage of the modifier is the high content of partially degraded rubber crumb (the state of partial decay of the vulcanization network in rubber), the particles of which have a porous surface, which leads to partial absorption of oil from bitumen, and, accordingly, to premature destruction of asphalt concrete.

Known modifier of bitumen (Patent RU 2349616, publ. March 20, 2009), which includes bitumen, a polymer additive and a rubber product regenerate (RTI), fuel oil and / or tar, organic peroxide (dicumyl or benzoyl peroxide) and a polymer additive - polyamide. As the mentioned regenerate, a regenerate obtained by the method of thermomechanical destruction of crumb rubber products in a screw disperser and containing rubber fractions with a molecular weight M _w from 18000 to 22000 conv. units - at least 10%, with the following ratio of components, _wt %: bitumen 15-18, polyamide 3-9, tar and / or fuel oil 15-20, organic peroxide 5-8, RTI regenerate - the rest is up to 100. The modifier allows you to increase elasticity of bitumen while increasing adhesion to the filler. Significant disadvantages of this modifier is the great complexity and energy consumption of its preparation due to the multi-stage process, the strong stickiness of the finished product, due to the content in the rubber regenerate of low molecular weight fragments of rubbers with molecular masses M _w not exceeding 22,000 srvc. units The strong stickiness of the modifier does not allow to obtain an acceptable commodity form of the modifier for its industrial production.

As a prototype of the first object of the invention adopted elastomeric modifier "Elastdor", described in the doctoral dissertation Shahovets S.E. “Integrated mechano-thermochemical regeneration of tire waste and the technology for the production of products based on them” 05.17.06, St. Petersburg, 2008, pp. 82-88, 97-104, 245-246 [the text of the dissertation is available on the website www.dissercat. com]. The Elastdor modifier is a regenerate obtained from a large 5-10 mm crumb of depreciated tires or from crumbs of waste products from rubber products during the regeneration process on a rubber regeneration machine, which is based on a worm destructor. In the destructor, two high-temperature processes occur simultaneously - activated mechanothermal destruction and steam destruction, that is, intense mechanical shear stresses are created and, at the same time, the destruction process can be activated with acute steam. The crumb rubber is degraded to particles of molecular size, which are able to interact with the molecular fragments of bitumen with the formation of a grid. The manufacturing process of the modifier determines its following physicochemical characteristics: content of the gel fraction 67.4-74.8%, content of the sol fraction 32.6-25.2%, molecular weight of the rubber in the ash mass-average (M _w ) 36100- 46900 conv. units, mass fraction of rubber, not less than 45%. The presence of low molecular weight fractions in the modifier leads to high stickiness, which makes it difficult to feed it into hot bitumen and subsequent mixing of the components. The preparation cycle of rubber-bitumen binders is 5-6 hours, which leads to aging of bitumen and a decrease in the quality of binders. The prototype modifier has the following properties: Mooney viscosity 25-30 srvc. units, density 1.10-1.12 g / cm ³ , conditional tensile strength 4.6-5.2 MPa, elongation 125-165%.

In road construction, polymer-bitumen binders based on block copolymers of the styrene-butadiene-styrene type (SBS) are used. A often used polymer-bitumen binder is PBV-60, corresponding to GOST R 52056-2003. Polymer-bitumen binders (PBB) are prepared on the basis of viscous road bitumen, the introduction of block-copolymers SBS, plasticizers and surfactants. SBS block copolymers improve the physicomechanical characteristics of petroleum bitumen, but are expensive modifiers made from primary raw materials.

As a prototype for the second object of the invention, a binder, composite bitumen binders “BITREK” are adopted, described in the standard of the organization STO 58528024.001-2013 (LLC “Scientific and Production Group“ Information and Technologies ”), [information can be found on the Internet at: http://rosavtodor.ru/storage/b/2015/01/20/sto_58528024_001_2013.pdf], which, as noted in the service station, was developed on the basis of patents RU 2167898 and RU 2178434. In these patents, a rubber-bitumen binder “BITREK” is presented, representing petroleum bitumen modified with fine rubber new crumb (from shock-absorbed tires) with particle sizes less than 0.63 mm, subjected to heat treatment in the presence of a complex of reagents and catalysts based on nitroxyl, triphenylmethyl compounds of the metals cobalt, vanadium, nickel, etc. At the first stage, a modifying composition is made of road bitumen, for example, BND 90/130, with the addition of 7-10% _{mass of} tire crumbs with particle sizes up to 0.5 mm, which are mixed in a mixer (i.e., without creating pressure in the reaction chamber) at a temperature 180-200 ° C until swelling and surface destruction of crumbs. Reagents and catalysts are added to the mixture and mixed. In this system, thermochemical reactions occur, as a result of which free radicals are formed, which interact with bitumen with the formation of a heterogeneous reinforcing structure in bitumen. Then add the original bitumen and mix. It should be noted that BITREK provides improved properties of oil bitumen in a freshly prepared state. In the BITREK binder, rubber is an undissociated or poorly dissociated vulcanization network, which is a flexible polymer frame throughout the volume of the material. The grid is sparse, therefore, on the other hand, the plastic properties of bitumen are preserved, the components of which are built into this grid, so the liquid phase of bitumen is enclosed in a spatial macrogrid. In such a composition, targeted additives are well retained, including those previously present in rubber. This favorably affects a number of properties - resistance to oxidation, aging, weathering.

However, the high-temperature thermochemical process and the long production cycle lead to intensive aging of bitumen during the manufacturing process of the binder and, consequently, to a decrease in the interval of plasticity of the binder.

Another significant drawback of the BITREK binder is its inhomogeneity, since it contains surface-degraded rubber crumb (up to 10%). The presence of crumb rubber in asphalt leads to its premature destruction, since the crumb partially absorbs the maltene component of bitumen.

Ultimately, the presence of surface-degraded rubber crumb in the binder leads to the fact that it does not have sufficiently high values of hardness, softening temperature and elasticity, and a relatively high brittle temperature, which is directly related to the binder, and then to the corresponding indicators of the asphalt concrete or other a coating made using a binder.

The basis of the invention is the task of expanding the arsenal of funds by creating a new elastomeric modifier of oil bitumen, obtained exclusively (that is, without the use of reagents and catalysts) from the regenerated crumb of rubber products, in particular from shock-absorbed tires (the so-called tire crumb), as well as a new elastomer bitumen binder with its use. The technical result achieved is an improvement in the complex of consumer properties of an elastomer-bitumen binder, namely an increase in hardness, softening temperature, elasticity and a decrease in the temperature of brittleness, and, accordingly, an improvement in the performance of asphalt concrete obtained using a binder.

The problem in the first object of the invention is solved in that the elastomeric modifier of oil bitumen is characterized by the fact that it is a granular regenerate of crumb rubber products, preferably crushed rubber from shock-absorbed tires, the so-called tire regenerate having the following characteristics: content of gel fraction 73-85 %, mass-average molecular weight of rubber in ash 87500-131600, conv. units, mass fraction of rubber at least 50%.

Preferred is the manufacture of granules with sizes of 0.5-1.0 mm It is also possible to produce granules of the aforementioned size and / or their agglomerates with a maximum size of 10-12 mm.

The problem in the second object of the invention is solved in that the elastomer-bitumen binder is characterized in that it includes the inventive elastomeric modifier of oil bitumen and oil bitumen, with the following ratio of components,% _mass :

an elastomeric modifier (preferably granular crumb regenerate rubber products - tire regenerate) 5-25 - oil bitumen - the rest is up to 100.

The claimed elastomeric modifier is prepared as follows.

Pre-crushed rubber products, for example, shock-absorbed tires, crushed to a state of crumbs with a particle size of 3-6 mm, are metered into a screw dispersant-devulcanizer, which has tapered slot sections between the body and sections of the screw shaft that divide the inner space of the dispersant-devulcanizer into two technological zones. The baby, passing through the first technological zone, undergoes surface devulcanization under the influence of pressure and dissipation heating in a narrow conical gap. At the exit from the first zone, the uniformity of the fractional composition also increases. Then, during transportation by the second section of the feed screw, partially devulcanized crumb enters the second processing zone. Transportation is accompanied by recycling of the material, and the heating temperature is maintained within a range not exceeding the pyrolysis temperature, due to heat transfer to the water-cooled casing and the screw. In the second technological zone, the final devulcanization of the material takes place: under the influence of compression and shear forces in the second technological zone, the particles of rubber crumb undergo dissipation heating and bulk devulcanization, the sulfur and carbon-carbon bonds of rubber macromolecules are destroyed, and the polymer reactive centers appear. The temperature in the second technological zone is set in the range of 170-230 ° C. At temperatures below 170 ° C, the process of devulcanization of rubber crumb occurs only on the surface, and not in the volume of crumb particles. At temperatures above 230 ° C, the destruction of rubber macromolecules with intense breaking of carbon-carbon bonds begins to prevail, which leads to a decrease in the molecular weight of the polymer and a sharp deterioration in the physicomechanical properties of the regenerates.

To obtain a high-quality elastomeric modifier, its temperature during unloading from the second technological zone should not exceed 180 ° C in order to optimize the influence of the above factors.

From the dispersant-devulcanizer, the regenerate obtained in the form of granules enters the cooling device. A rapid decrease in the temperature of the regenerate contributes to the cessation of the devulcanization reaction. The granules of the elastomeric modifier obtained in the dispersant-devulcanizer, cooled in it to a temperature of 80 ° C, are fed into a counter-current air cooler, in which due to convective cooling with air the modifier is cooled to a temperature not exceeding 30 ° C, and at the same time the granules are dusted due to supply of mineral powder, for example, dolomite flour, chalk, etc. Thus, the new modifier was obtained in industrial conditions by exclusively optimizing technological conditions: a combination of conditions with Denmark degrades pressure and temperature values specified in the process zones inner space devulcanizer dispersant, i.e., obtained without introducing reactants and catalysts.

Since the screw dispersant-devulcanizer itself and the cooling device are not the subject of the present invention, their design is not given.

The improved performance of an elastomeric modifier of petroleum bitumen based on a rubber regenerate is explained by the fact that as a result of mechanothermal devulcanization, a spatially crosslinked rubber network is controlled to break down within a short period of time (5-7 minutes), mainly by carbon-sulfide bonds with the appearance of unsaturated double bonds. At the same time, the destruction of carbon-carbon bonds occurs with a decrease in the length of the rubber macromolecules and the appearance of reactive radicals. This is evidenced by the results of a study of the molecular composition, macro- and microstructure of rubbers in samples of elastomeric modifiers by gel permeation chromatography on a Waters gel chromatograph. Characteristics and properties of the inventive elastomeric bitumen modifier are presented in Table. 1 and are given in comparison with the modifier of the prototype (modifier "Elastdor"). A significant variation in the values of the indicators of the declared modifier is explained by differences in the starting material: tread crumb or crumb of sidewalls, domestic brands or foreign, or it is crumb of waste from the production or processing of rubber products, etc., that is, it is determined primarily by the chemical composition of the feedstock - crumbs, as well as its fractional composition and specific technological modes (devulcanization temperature, pressure, cooling rate). However, it is within the limits of the obtained and claimed intervals that the new product exhibits improved properties with respect to the prototype and analogues.

As can be seen from Table. 1, the claimed modifier contains 73-85% of the gel fraction responsible for creating a mesh structure in bitumen, which is 5.6-10.2% more than the modifier of the prototype obtained from similar rubbers, and the molecular weight M _{w of the} degraded rubbers that give stickiness to the modifier in the sol fraction are 2.4-2.8 times less than in the prototype.

The higher content of rubber gel in the inventive modifier compared with the prototype indicates less destruction of the macromolecular network and, accordingly, the possibility of obtaining improved structure and properties of a bitumen binder. A 1.5-fold decrease in the average sol-fraction and a change in the molecular structure — a shift towards high-polymer molecules (M _w = 87500-131640 units) in the inventive modifier, ensured a decrease in stickiness, and, accordingly, made it possible to obtain the modifier in granular form with dimensions granules of 0.5-1.0 mm and / or their agglomerates with the largest size of 10-12 mm, that is, to provide a marketable form acceptable for use in the existing technology of asphalt concrete plants.

Studies of the properties of the elastomeric modifier according to physicochemical parameters were carried out on test samples. Samples were made from a test mixture per 100 g of elastomeric modifier:

- sulfenamide C 0.8 g - zinc oxide 2.5 g - stearic acid 0.33 g - sulfur 1.2 g

The production of test mixtures was carried out on laboratory rollers. The curing of the test plates was carried out in a curing press at a temperature of 145 ° C for 15 minutes. Mooney viscosity was measured on samples of an elastomeric modifier on a MZ -4016 B1 Moony viscometer.

The molecular characteristics of the elastomeric modifier were determined by gel permeation chromatography on a Waters gel chromatograph.

As can be seen from Table. 1, the physico-mechanical properties of the inventive elastomeric bitumen modifier, such as Mooney viscosity, density, conditional tensile strength, elongation, significantly exceed the characteristics of the prototype.

An elastomer-bitumen binder for asphalt mix using granular elastomeric modifier based on tire regenerate was made on a multi-pass installation of MASSENZA, Italy. Bitumen, for example, the widely used BND 70/100 (minimum operating temperatures in the cold season, according to GOST 33133-2014, from minus 10 ° С to plus 5 ° С), heated to a temperature of 170-175 ° С and the above-described granular elastomeric the modifier was loaded into a pre-mixer equipped with two propeller mixers in percentages by weight, respectively: 90:10, 85:15, 80:20, depending on the technical requirements for an elastomer-bitumen binder, and mixed.

At this stage, the swelling and partial dissolution of the modifier in bitumen occurred on average for one hour. After that, a mixture of bitumen with a modifier was passed through a colloidal mill, pumping it to a second mixer, also having two mixers. At least 4 runs were performed until a uniform binder was obtained. The duration of each run was 8-10 minutes. Then the finished elastomer-bitumen binder was pumped into containers with mixers for ripening for at least one hour.

As can be seen from the above, the binder is obtained from two components - from bitumen and regenerated crumbs of rubber goods, which is completely devulcanized, that is, the rubber itself is no longer. However, this binder cannot be attributed to rubber, in the sense as is customary in the art, since it is not made of synthetic rubber. Therefore, in this case, the use of the term "rubber-bitumen binder" or "bitumen-rubber binder", widely used in the technical literature, does not apply to this product. In this application, the term elastomer-bitumen binder is used, as the most fully reflecting its essence.

In contrast to the known binders based on synthetic rubbers, in the manufacture of the inventive binder it is not necessary to add plasticizers, for example, petroleum oils such as PN-6sh, stabiloplast-62, etc., since the necessary additives are contained in the initial crumb and, accordingly, in the elastomeric bitumen modifier. In addition to plasticizers, the claimed elastomeric modifier contains technical carbons, silicic acid components (white soot), chemical stabilizers and antioxidants that slow down the aging process of the binder and help to increase the service life of the asphalt concrete pavement that was originally contained in crumbs. Thus, the use of elastomeric bitumen modifiers based on regenerates of rubber products does not require any conversion of plants to produce binders based on modified bitumen and also does not require chemical additives.

In Tab. 2 presents the physico-mechanical properties of the inventive elastomeric-bitumen binder in comparison with the prototype and analogue (polymer-bitumen binders based on thermoplastic elastomer SBS L 30-01 A).

The indicator of the formation of a polymer skeleton in bitumen in the production of rubber-bitumen binder is the dynamic viscosity of the system. As follows from the table. 2, the properties of an elastomer-bitumen binder - the dynamic viscosity of the inventive binder with an elastomeric modifier is 1.56-1.83 Pa / s and is 16-20% higher than the dynamic viscosity of the binder PBV-60 (1.34 Pa / s). Also seen from Tab. 2, that all of the above indicators are higher than that of the given analogue and prototype. A binder based on an elastomeric modifier has a plasticity interval (algebraic difference between softening and brittle temperatures) of more than 100 ° C, in which bitumen is in a visco-plastic state and provides the best construction and operational properties of asphalt concrete. This indicator is better than that of the prototype binders (BITREK) (80 ° C) and the analogue of PBV-60 (74 ° C). The high elasticity of the inventive binder (at 25 ° C, component 72-83%) also indicates the presence of a spatial elastic structural network of the polymer in the binder and characterizes its high resistance to repeated dynamic effects and a decrease in the formation of fatigue and temperature cracks on the road surface.

In Tab. 2 gives examples of indicators of an elastomeric-bitumen binder made using granular regenerate of crumb rubber products as an elastomeric modifier and bitumen BND70 / 100. However, it is possible to use other viscous road petroleum bitumen according to GOST 33133-2014. The experiments carried out confirmed that the improvement of the indicators given in Table. 2 in comparison with the prototype and analogue is achieved, depending on the brand of bitumen used, with the addition of 5-25% of the modifier. In the patented invention, the manufacturing temperature of the elastomer-bitumen binder is reduced by at least 10 ° C compared with the manufacture of a binder according to the prototype. In addition, the total cooking time of the binder is also reduced from 5 hours to 3 hours. These two factors reduce bitumen aging in the asphalt mix manufacturing cycle, which leads to an increase in the durability of the asphalt concrete pavement. The granular form of an elastomeric modifier with granule sizes of 0.5-1.0 mm and / or agglomerates of these granules with the largest size of 10-12 mm allows you to evenly distribute the modifier in the volume of bitumen and homogenize the resulting binder, which also positively affects the claimed result. In addition, this form is convenient for transportation and storage, and use in asphalt concrete and other plants for the industrial production of binder on technological equipment used to produce polymer bitumen binders.

Claims (6)

1. The elastomeric modifier of petroleum bitumen, characterized in that it is a granular regenerated crumb rubber products with the following characteristics: the content of the gel fraction 73-85%, the mass-average molecular weight of the rubber in the ash 87500-131600 srvc. units, mass fraction of rubber at least 50%. 2. The elastomeric modifier of petroleum bitumen according to claim 1, characterized in that said regenerate is a tire regenerate. 3. The elastomeric modifier of petroleum bitumen under item 1 or 2, characterized in that the regenerate is a granule with a size of 0.5-1.0 mm and / or represents agglomerates of these granules with a largest size of 10-12 mm 4. Elastomer-bitumen binder, characterized in that it contains an elastomeric modifier of oil bitumen, which is a granular regenerated crumb rubber products according to claim 1, and oil bitumen, in the following ratio of components, wt.% : said elastomeric modifier 5-25 oil bitumen the rest is up to 100 5. The elastomer-bitumen binder according to claim 4, characterized in that said regenerate is a tire regenerate.